This invention relates to a cover-terminal assembly for an electrolytic capacitor. More particularly, it relates to an assembly with improved weight-loss characteristics.
Electrolytic capacitors that are designed for operation at 85.degree. C.-125.degree. C. or higher frequently employ dimethylformamide as electrolyte solvent. Its high solvency requires the use of chemically-inert materials for covers and gaskets. Polypropylene and other low softening temperature plastics have been used to make such covers. Such materials are described by Zeppieri in U.S. Pat. No. 3,398,333, issued Aug. 20, 1968, and are chemically-resistant and resilient enough to permit bonding of the terminal to the cover by an upset operation. However, some of these materials, and particularly polypropylene, suffer weight loss on temperature cycling due to relaxation of the polypropylene at elevated temperatures. Desirable properties for a cover material include the absence of volatile or degradable constituents so as to insure low or no weight loss on temperature cycling, chemical resistance to high solvency electrolyte solvents, ease of manufacture by conventional processes such as molding, and ease of bonding to terminals and capacitor containers to provide a leak-proof unit.